UiO-66-functionalized Sandwich Composite Separators for Improved Performance and Safety of Lithium-ion Batteries

Thermal runaway-induced safety issues have seriously hindered further development of lithium-ion batteries (LIBs). As a key component of LIBs, high-performance electrospun nanofiber separators (ENSs) with high-temperature self-closing functions can prevent safety issues caused by thermal runaway in LIBs. In this study, a sandwich-structured high-temperature self-closing polyacrylonitrile/polyurethane//adding cetyltrimethylammonium bromide to the poly(butylene succinate) (PAN/PU//CPBS) ENS (CPC ENS) was efficiently fabricated using free-surface electrospinning technology via material selection and structural design. A high-melting-point polyacrylonitrile-based ENS served as the intermediate layer, providing its thermal stability, while a low-melting-point polybutylene succinate-based ENS served as the outer layer, endowing it with a high-temperature self-closing function. To enhance its performance, CPC ENS was modified with polydopamine and loaded with porous structured UiO-66 rich in active sites, resulting in a high-performance self-closing UiO66@PDA@CPC ENS. The results showed that UiO66@PDA@CPC ENS had an excellent electrolyte uptake rate (740.7%±20.6%) and wettability (8.3°±0.3°), while maintaining good thermal stability at 160 °C. Furthermore, after 100 cycles at 0.5 C, the assembled battery maintained a discharge specific capacity of 139.6 mAh/g, with a capacity retention rate of 92.4%. Meanwhile, the surface of the lithium sheet had a flat morphology, indicating that UiO66@PDA@CPC ENS had superior long-term cycling stability, thus demonstrating its enormous potential as a high-performance and safe LIB separator.